Emulsifiers for butadieneacrylonitrile copolymerisation



Patented July 3, 1956 EMULSIFIERS FOR BUTADIENEA'CRYLONITRILE COPOLYMERISATION Application August 22, 1952, Serial No. 305,926

Claims priority, application Canada August 19, 1952 9 Claims. (11. 260-825) No Drawing.

This invention relates to improvements in the choice of emulsifier in the copolymerisation of butadiene-1,3 and acrylonitrile using a water soluble persulfate catalyst and a water soluble ferrous promoter and carried on at temperatures below 85 F.

An inexpensive and convenient emulsifier for such emulsion polymerisation of butadiene-1,3 and acrylonitrile is a natural potassium fatty acid soap. Moreover, the natural potassium fatty acids appear to increase the effectiveness of the ferrous promoter and hence give an improved rate of conversion. The disadvantage of such emulsifiers is that, on acidification to break the latex, the residual soap or fatty acids become insoluble in water and are precipitated with the polymer. These components thus form impurities in the rubber which are considered a distinct disadvantage in that they are reputed to increase the absorption of water by the polymer and reduce the quality of the polymer for electrical purposes. Moreover, where the polymer is employed in fuel cells the fatty acids are believed to be extracted from the rubber and result in the formation of gum in the gasoline.

Unfortunately, it has been found that reduction of the proportion of such natural soap used in order to reduce the excess which forms the insoluble impurities serves substantially to reduce or eliminate its efficiency both as an emulsifier and as an auxiliary promoter.

These disadvantages render these natural soap emulsifiers much less desirable and the choice or selection of a low cost synthetic emulsifier which remains water soluble on acidification offers advantages. While such synthetic emulsifiers are satisfactory if the temperature of reaction is maintained at 85 F. or above, the rates of reaction at temperatures appreciably below that temperature are inadequate for commercial operations. Moreover, the synthetic emulsifiers do not appear to possess the auxiliary promoting properties of the said natural soaps.

It is the object of this invention to provide inexpensive and convenient emulsifiers which give satisfactory rates of polymerisation below 85 F. without deposition of appreciable quantities of soap curds on acidification.

The present invention is based on our discovery that a mixture of a water-soluble synthetic emulsifier and potassium palmitate or stearate shows a synergistic action. As stated above in connection with natural soap generally, a proportion of potassium palmitate or stearate, which is made small enough to avoid substantial precipitation of the excess, will not affect efficient emulsification and auxiliary promotion. If, however, such small proportion of potassium palmitate or stearate is used in conjunction with a major proportion of synthetic emulsifier, all three advantages are obtained, namely, no appreciable precipitation of soap, efiicient emulsification of the reaction mix and auxiliary promotion of-the rate of reaction.

According to the present invention, therefore, the copolymerisation of the type stated is carried out in the presence of an emulsifier which comprises a major proportion of a synthetic emulsifier which remains water soluble on acidification and a minor proportion of potassium palmitate or stearate.

The combined emulsifier will generally be used in a proportion of at least 3 parts by Weight per parts of polymeric material. Also based on 100 parts by weight of polymeric material, the preferred minimum proportion for the potassium palmitate is 0.3 part and for the potassium stearate is 0.1 part. The preferred maximum proportion of potassium palmitate or stearate is that proportion which will be just insufficient to cause appreciable precipitation, e. g. 2 parts.

The synthetic emulsifier may be of any suitable type provided that it is water soluble. A common type which may be used is the sulfated fatty alcohol type, which includes derivatives thereof.

It is to be realized that the potassium palmitate or stearate may be employed alone or in combination, e. g. in the form of commercial soap which generally contains both.

The following examples are given for the purpose of illustration, the parts being by Weight:

EXAMPLE I The basic recipe for conventional butadiene-acrylonitrile reactions of the type specified is as follows:

Parts Butadiene-l,3 64 Acrylonitrile 36 Water 250 K2S20s 0.270 FSO4.7H2O 0.278 Mixed tertiary mercaptans 0.700 KOH 0.140 Potassium fatty acid soaps 5.00

Such a charge was reacted at 41 F. for 20 hours at which time the reaction was stopped by the addition of 0.200 parts of hydroquinone added as a 5% aqueous solution. 48% conversion was determined to have been achieved. When the 5 parts of potassium. fatty acid soap in the recipe were omitted and a synthetic emulsifier comprising 4 parts of a mixed alkylated naphthalene sulfonate condensed with formaldehyde (sold under the registered trademark Daxad 12 K) and 1 part of an alkyl aryl sodium sulfonate (sold under the registered trademark Naccanol NRSF) was substituted, the conversion achieved after reacting for 20 hours at 41 F. was only 5%. The KOH was reduced slightly to 0.100 to maintain the same pH.

The reduced rate of reaction achieved when synthetic emulsifiers are used in lieu of potassium fatty acid soaps demonstrates that such a substitution in the recipe would be quite unsatisfactory regardless of the improvement in the product. When, however, the emulsifier is predominantly synthetic emulsifier and only a minor proportion is fatty acid, the combination results in what is believed to be a superior product and the rate of reaction is appreciably enhanced, as will be illustrated in the further examples.

EXAMPLE II The general recipe set out in Example, I except for one variation, was employed in a number of tests. The 5 parts of K fatty acid soaps were omitted and 3 parts Daxad 12 K and 1.0 part of the indicated emulsifier were substituted as an emulsifier. The monomers, viscosity regulator, and emulsifiers were prepared as an. alkali solution with the KOH added to adjust the pH. The reaction is initiated by the addition of firstly 1(28403 and secondly FeSOMHzO. In each case the charge was permitted to react for 17 hours at 41 F. The percentage conversion achieved in each case was as set out in Table 1.

The marked advantage to be gained by using K palmitate or K stearate, or commercial mixtures containing them is, however, manifest. Equivalent Weights of the other fatty acid soaps show much inferior results.

The quantity of the potassium palmitate or stearate employed may be varied within certain limits to meet the conditions of the reaction. or product as desired. The following example serves to demonstrate the effect of reducing the quantity below the 1.0 part used in Example II.

EXAMPLE Ill Employing the basic recipe and the practice set out in Example II the experiments were repeated using the various amounts of the fatty acid soaps as indicated. The samples were reacted for 17 hours at 41 F. The percent conversion achieved in each case is set out in Table 2.

Table 2 Pts./Wt 0.20 0.40 0.60 0.80 1.00

Per- Per- Per- Per- Percent cent cent cent cent K Neofat 7 (Reg. T. M.) 46.8 35.1 35.5 29.2 46. 6 43. 40. 5 66. 0 50. 0 51. 0 42. 2 3. 3 84. 3 78.1 81. 7 80.6 9.6 92.1 90.0 91.7 91.1 K Fatty acid soap 1 (commercial 3. 6 G1. 6 70. 9 82.9 60.4 K Fatty acid soap (commercial). 0. 8 41.1 45. 3 49. 3

1 The two groups of commercial fatty acid soaps varied only in the nature of the dispersing agent present. In the latter case a dispersing agent was employed which introduced substantial quantities of sodium salt. It is well known that sodium systems reduce the rate of reaction.

We claim:

1. A process for the emulsion copolymerisation below 85 F. of but-adienc-l,3' and acrylonitrile with a water soluble persulfate catalyst and a water soluble ferrous pro moter in which an emulsifier is employed comprising a major proportion of a sulfonated synthetic emulsifier which remains water soluble on acidification and a minor proportion of a natural soap selected from the group consisting of potassium palmitate and potassium stearate.

2. A process for the emulsion copolymerisation below F. of butadiene-1,3 and acrylonitrile with a water soluole persulfate catalyst and a water soluble ferrous promoter in which an emulsifier is employed comprising a major proportion of a sulfonated synthetic emulsifier which remains water soluble on acidification and a minor proportion of a natural soap selected from the group consisting of potassium palmitate and potassium stearate, the emulsifier being in a proportion of at least 3 parts by weight per parts of polymeric material.

3. A process for the emulsion copolymerisation below 85 F. of butadienel,3 and acrylonitrile with a water soluble persulfate catalyst and a water soluble ferrous promoter in which an emulsifier is employed comprising a major proportion of a sulfonated fatty alcohol and a minor proportion of a natural soap selected from the group consisting of potassium palmitate and potassium stearate.

4. A process for the emulsion copolymerisation below 85 F. of butadiene-1,3 and acrylonitrile with a water soluble persulfate catalyst and a Water soluble ferrous promoter in which an emulsifier is employed comprising a. major proportion of a mixed alkylated sulfonate condensed with formaldehyde and a minor proportion of a natural soap selected from the group consisting of potassium palrnitate and potassium stearate.

5. A. process as claimed in claim 1 in which the natural soap is potassium palmitate in a proportion of at least 0.3 part by weight per 100 parts of the polymeric material.

6. A process as claimed in claim 1 in which the natural soap is potassium stearate in a proportion of at least 0.1 part by weight per 100 parts of the polymeric material.

7. A process as claimed in claim 2 in which the natu ral soap is potassium palmitate in a proportion of at least 0.3 part by weight per 100 parts of the polymeric material.

8. A process as claimed in claim 2 in which the natural soap is. potassium stearate in a proportion of at least 0.1 part by weight per 100 parts of the polymeric material.

9. A process as claimed in claim 1 in which the ferrous promoter is ferrous sulfate.

References Cited in the file of this patent UNITED STATES PATENTS 2,386,764 Zwicker Oct. 16, 1945 2,538,273 Rhines Jan. 16, 1951 2,589,919 Arundale et al Mar. 18, 1952 2,595,892 Schulze et al May 6, 1952 2,623,032 Banes et a1. Dec. 23, 1952 

1. A PROCESS FOR THE EMULSION COPOLYMERISATION BELOW 85* F. OF BUTADIENE-1,3 AND ACRYLONITRILE WITH A WATER SOLUBLE PERSULFATE CATALYST AND A WATER SOLUBLE FERROUS PROMOTER IN WHICH AN EMULSIFIER IS EMPLOYED COMPRISING A MAJOR PROPORTION OF A SULFONATED SYNTHETIC EMULSIFIER WHICH REMAINS WATER SOLUBLE ON ACIDIFICATION AND A MINOR PROPORTION OF A NATURAL SOAP SELECTED FROM THE GROUP CONSISTING OF POTASSIUM PALMITATE AND POTASSIUM STEARATE. 